Transition Metal Ions in the Gas Phase

Effect of kinetic and electronic energy on the reactions of Ti + with H 2, HD, and D 2

DFT calculations are used to address the mechanism of Ni-catalyzed esterification of aryl and alkyl amides. The insight of the tailor-made catalysts in the chemo-selectivity is addressed in this work. The reaction steps for esterification of aryl and alkyl amides catalyzed by both Ni(SIPr)2 and Ni(terpyridine)2 include: oxidative addition, metathesis, and reductive elimination processes. Ni(SIPr)2 can catalyze the esterification of aryl amides rather than Ni(terpyridine)2 due to high reaction barrier in oxidative addition process, while Ni(terpyridine)2 can catalyze the esterification of alkyl amides rather than Ni(SIPr)2 due to high reaction barrier in metathesis process. It is found that the charge distribution on Ni is different in these two complexes. An amino-substituted terpyridine Ni complex is designed to catalyze both aryl and alkyl amides through low transition-state energies because of the electron-donating ability of three amino substitutes. The results reveal that the chemo-selectivity is mainly controlled by the electron-donating ability of ligands.

Metal/insulator interfaces are essential structures in most of electronic and optical devices, and thus the stability of such interfaces is important for the reliability of devices. It has long been known that the metal atoms in a gate electrode often penetrate into insulators by thermal diffusion during the annealing processes in device fabrication. In addition, metal atoms are ionized and such diffusion is remarkably enhanced under electric fields during device operation. Diffusing metal atoms often produce defect electronic states, promote leakage currents, and cause serious damage in electronic devices, particularly in recent nanoscale devices such as metal nanodot memories. On the other hand, such diffusion behavior is positively utilized to produce metal nanowires in insulators for resistive switching memory applications. However, the microscopic understanding of ionization and diffusion of metal atoms has not been obtained yet. In this work, we employ the first-principles calculations and clarify how metal atoms are ionized and diffuse under electric fields around metal/insulator interfaces. We consider metal/insulator interfaces made of a variety of metals (Al, Ag, Au, Pt, Ta, W, etc) and crystalline/amorphous SiO2. Electronic structures, ionic charges, and adiabatic diffusion potentials of metal atoms are evaluated using the first-principles calculations in the density functional theory. Electric field is applied perpendicular to the interface by supplying positive/negative electric charges to the interface-slab systems.With respect to the ionization, we found that the ionic charge of metal atom in SiO2 changes depending on the distance from the interface [1]. In a 0-6Å region near the interface, the diffusing atom is sharply ionized with leaving the interface. This occurs owing to the breakdown of orbital hybridization between electronic states of metal atom and metal induced gap states (MIGS) of metal electrode [2,3]. When the substrate is changed to semiconducting Si and Sn, this region is extended to 10-15Å. Outside this MIGS-penetration region, on the other hand, the ionic charge of metal atom still varies. This variation occurs due to the electron transfers from diffusing metal atom to not only surrounding SiO2 but also metal electrode. In this way, we can conclude that the ionization of the metal atom first begins quantum mechanically in the MIGS-penetration region and then its ionization charge changes electromagnetically outside the MIGS-penetration region.With respect to the diffusion under electric field, we found that the diffusion barrier linearly decreases with increasing the electric field. This result indicates that the electric field remarkably enhances the metal-atom penetration probability into SiO2, like an exponential function of electric field. Such enhancement works effectively for metal atoms with small electronegativity and mainly in the case of positive voltage application, which is in good agreement with observations. This is because most metal atoms prefer to ionized positively in insulators and small-negativity atoms have large ionic charges. These results are discussed in details, together with reviewing recent experiments, comparing to the cases of metal/semiconductor interfaces, and focusing on the fundamental physics of ionization and diffusion. <references> [1] Y. Asayama et al., Materials Science in Semiconductor Processing, DOI: 10.1016/j.mssp.2016.09.010 (2016). [2] T. Hiramatsu et al., Jpn. J. Appl. Phys. 53, 058006 (2014).[3] S. Sasaki and T. Nakayama, Jpn. J. Appl. Phys. 55, 111302 (2016). Figure 1

Chapter 6 - Multi-Functionality of Spintronic Materials

Transparent materials based on semiconducting ZnO: glass-ceramics and optical ceramics doped with rare-earth and transition-metal ions

Transition metal (TM) ion activated phosphors are increasingly being used as probes for luminescence thermometry. Their luminescence is characterized by strong absorption and emission bands that span the visible and near-infrared spectral ranges and are highly susceptible to temperature variations. Due to the latter characteristic, sensitive and reliable remote temperature measurements can be performed by observing temperature-induced changes in TM ion emission intensities, emission bandwidths and bandshifts, and excited state lifetimes, as well as the temperature dependences of the intensity ratios between various emission bands in single or double activated phosphors. This review provides a systematic analysis of the performances of luminescent thermometers based on different TM ions and discusses the relations among the TM spectroscopic properties, characteristics of the host material structure, and thermometric performance. Particular attention is given to the engineering of energy transfer between TM and other dopant ions to obtain highly sensitive thermometers. Finally, several typical application examples from recent literature are highlighted.

The individual steps of a model Pd-catalyzed Negishi coupling between vinyl bromide and MeZnClS2 (S = THF), using Pd(PMe3)2 as catalyst, have been examined with the aid of DFT computations in THF solution with the B97D functional to gain further insight into the role of Pd–Zn interactions on the oxidative addition and reductive elimination steps. Comparisons between such processes taking place on monometallic Pd complexes and on bimetallic Pd–Zn complexes reveal a detrimental effect of Pd–Zn interactions in oxidative addition, whereas reductive elimination is favored by Pd–Zn cooperativity. Additionally, a cis transmetalation pathway has been characterized that complements previous studies involving trans complexes.

Native mass spectrometry has emerged as an important tool for gas-phase structural biology. However, the conformations that a biomolecular ion adopts in the gas phase can differ from those found in solution. Herein, we report a synergistic, native ion mobility-mass spectrometry (IM-MS) and transition metal ion Förster resonance energy transfer (tmFRET)-based approach to probe the gas-phase ion structures of a nonstapled peptide (nsp; Ac-CAARAAHAAAHARARA-NH2) and a stapled peptide (sp; Ac-CXARAXHAAAHARARA-NH2). The stapled peptide contains a single hydrocarbon chain connecting the peptide backbone in the i and i + 4 positions via a Grubbs ring-closure metathesis. Fluorescence lifetime measurements indicated that the Cu-bound complexes of carboxyrhodamine 6g (crh6g)-labeled stapled peptide (sp-crh6g) had a shorter donor-acceptor distance (rDA) than the labeled nonstapled peptide (nsp-crh6g). Experimental collision cross-section (CCS) values were then determined by native IM-MS, which could separate the conformations of Cu-bound complexes of nsp-crh6g and sp-crh6g. Finally, the experimental CCS (i.e., shape) and rDA (i.e., distance) values were used as constraints for computational studies, which unambiguously revealed how a staple reduces the elongation of the peptide ions in the gas phase. This study demonstrates the superiority of combining native IM-MS, tmFRET, and computational studies to investigate the structure of biomolecular ions.

Recent progress on optical properties of double perovskite phosphors

Two‐electron oxidative addition is one of the most important elementary reactions for d‐block transition metals but it is uncommon for f‐block elements. Here, we report the first examples of intermolecular oxidative addition of E−H (E=C, N) bonds to uranium(II) centers. The transient U(II) species was formed in‐situ by reducing a heterometallic cluster featuring U(IV)‐Pd(0) bonds with potassium‐graphite (KC8). Oxidative addition of C−H or N−H bonds to the U(II) centers was observed when this transient U(II) species was treated with benzene, carbazole or 1‐adamantylamine, respectively. The U(II) centers could also react with tetracene, biphenylene or N2O, leading to the formation of arene reduced U(IV) products and uranyl(VI) species via two‐ or four‐electron processes. This study demonstrates that the intermolecular two‐electron oxidative addition reactions are viable for actinide elements.

Transition metal alloyed zinc oxide (ZnO) materials are promising candidates for spin-based electronics (spintronics) and optoelectronic applications. The interaction between the ZnO host lattice and the incorporated transition metal ions form the basis for these applications and can induce a ferromagnetic alignment of the transition metal spins with a Curie temperature above room temperature. On the other hand, the electronic structure of the 3d-shell of the transition metal ions is affected by the crystal field, spin-orbit and Jahn-Teller interaction with the ZnO host matrix. As a result, optical transitions between the 3d-shell states become partly allowed. The control of the transition metal concentration as well as the formation of secondary phases are the major issues not only for the preparation of transition metal alloyed ZnO single crystals and thin films but also for nanowires. Commonly ZnO nanowires are grown via the vapour liquid solid mechanism, which is discussed for ZnO nanowires with respect to the issues of the transition metal incorporation. Ion implantation after the growth of single crystals, thin films and nanowires is an alternative method for the controlled incorporation of transition metals into ZnO. However, ion implantation generates crystal defects, which are observed by an intensity increase of the A1(LO) phonon disorder band of as implanted ZnO. Annealing under air ambient at different temperature stages leads to an reduction of a major part of these defects. High dose transition metal implanted ZnO samples show after annealing some additional Raman modes and Bragg diffractions, which can not be assigned to ZnO. A detailed analysis of this signals reveals the formation of several transition metal rich segregations. On the other hand, photoluminescence and cathodoluminescence measurements show two new deep luminescence bands after transition metal ion implantation and annealing. The red-yellow luminescence band is assigned to interstitial oxygen defects with tetrahedral surroundings. The structured green luminescence band is commonly assigned to Cu impurities. However, the configuration coordinate model is used to explain the structured green luminescence band, whereby the structured green luminescence band is a superposition of two donor-acceptor transitions with the same deep acceptor and two different shallow donors. The chemical nature of the deep acceptor is assigned to interstitial oxygen on an octahedral site, and the two shallow donors are assigned to interstitial zinc on octahedral as well as tetrahedral sites. Co and Fe implanted ZnO samples show additional sharp luminescence lines, which are assigned to intra-3d-shell transitions of Co2+ and Fe3+ ions in the ZnO host lattice. The intensity of intra-shell luminescence increases almost linearly with increasing excitation power and exceeds the linear behaviour for excitation power densities above 300 mW/cm2, which suggest a transfer from spontaneous emission to stimulated emission.

Density functional and microkinetic study of CO2 hydrogenation to methanol on subnanometer Pd cluster doped by transition metal (M= Cu, Ni, Pt, Rh)

A Chemical Aqueous Phase Radical Mechanism (CAPRAM) for modelling tropospheric multiphase chemistry is described. CAPRAM contains (1) a detailed treatment of the oxidation of organic compounds with one and two carbon atoms, (2) an explicit description of S(IV)-oxidation by radicals and iron(III), as well as by peroxides and ozone, (3) the reactions of OH, NO 3 ,C l 2 , Br 2 ,a nd CO 3 radicals, as well as reactions of the transition metal ions (TMI) iron, manganese and copper. A modelling study using a simple box model was performed for three different tropospheric conditions (marine, rural and urban) using CAPRAM coupled to the RADM2-mechanism (Stockwell et al., 1990) for liquid and gas phase chemistry, respectively. In the main calculations the droplets are assumed as monodispersed with a radius of 1m and a liquid water content of 0.3 g m 3 .I n the coupled mechanism the phase transfer of 34 substances is treated by the resistance model of Schwartz (1989). Results are presented for the concentration levels of the radicals in both phases under variation of cloud duration and droplet radius. The effects of the multiphase processes are shown in the loss fluxes of the radicals OH, NO 3 and HO2 into the cloud droplets. From calculations under urban conditions considering gas phase chemistry only the OH maximum concentration level is found to be 5:5 10 6 cm 3 . In the presence of the aqueous phase (r D 1 m, LWC D 0: 3g m 3 ) the phase transfer constitutes the most important sink (58%) reducing the OH level to 1:0 10 6 cm 3 . The significance of the phase transfer during night time is more important for the NO3 radical (90%). Its concentration level in the gas phase (1:9 10 9 cm 3 ) is reduced to 1:4 10 6 cm 3 with liquid water present. In the case of the HO2 radical the phase transfer from the gas phase is nearly the only sink (99.8%). The concentration levels calculated in the absence and presence of the liquid phase again differ by three orders of magnitude, 6 10 8 cm 3 and 4:9 10 5 cm 3 , respectively. Effects of smaller duration of cloud occurrence and of droplet size variation are assessed. Furthermore, in the present study a detailed description of a radical oxidation chain for sulfur is presented. The most important reaction chain is the oxidation of (hydrogen) sulphite by OH and the subsequent conversion of SO 3 to SO 5 followed by the interaction with TMI (notably Fe 2C )a nd chloride to produce sulphate. After 36 h of simulation ((H2O2U0 D 1 ppb; (SO2U0 D 10 ppb) the direct oxidation pathway from sulfur(IV) by H2O2 and ozone contributes only to 8% (2:9 10 10 M s 1 ) of the total loss flux of S(IV) (3 :7 10 9 Ms 1 ).

Only a small number of Li-containing cathode materials groups are considered for practical use in Li-ion battery systems. The possible candidates of cathode material were limited to the crystals that contain both redox-active element and lithium ion in the open framework. This concept has been conventionally considered as a standard for searching the cathode materials. But, it could be constraints to restrict the choices of materials for cathode in Li-ion battery systems. To expand the sight for seeking new positive electrode material, we suggested a novel strategy to use various kinds of Li-free transition metal ionic compounds (MX, M = transition metal, X = anion or polyanion group) as a positive electrode material by blending with a Li ionic compound (LiY, Y = anion or polyanion group) in nanoscale.[1] MX and LiY provided a redox couple and lithium ion supply for an electrochemical reaction. This concept is unconventional with general system of electrode material (Li ions and transition metal ions are in the same crystal system). In this case, transition metal ion and Li ion in the nanocomposite do not exist in the same crystal system and spatially separated as a mixture of MX and LiY. In this paper, we will introduce and discuss about the transition metal oxide system as a redox couple among the infinite possible combinations of lithium ionic compounds and metal ionic compounds. Transition metal oxides such as FeO, MnO were considered as promising anode materials due to the earth abundance and large capacity from conversion reaction.[2] Although they have redox potential below 1 V as anode material,[3][4] we will show that this transition metal oxides can be applied to the cathode materials (3 V-class) by making nanocomposite with lithium ionic compound. To better understand the mechanisms during electrochemical cycling we have performed XPS, XANES/EXAFS analysis, allowing us to study the local environment change of Fe or Mn during the charge and discharge reaction. FeO and MnO showed different aspects during the electrochemical reaction in terms of electrochemical activity and local environment change. We will discuss about the reaction mechanism in detail.[1] S.-W. Kim, K-Y. Nam, D.-H. Seo, J. Hong, H. Kim, H. Gwon, and K. Kang, Nano Today, 7, 168 (2012)[2] P. Poizot, S. Laruelle, S. Grugeon, L. Dupont, and J.-M. Tarascon, Nature, 407, 496 (2000)[3] M. Gao, P. Zhou, P. Wang, J. Wang, C. Liang, J. Zhang, and Y. Liu, J. Alloy. Compd., 565, 97 (2013)[4] X. Li, D. Li, L. Qiao, X. Wang, X. Sun, P. Wang, and D. He, J. Mater. Chem., 22, 9189 (2012)

Gas-phase experiments with state-of-the-art techniques of mass spectrometry provide detailed insights into numerous elementary processes. The focus of this Review is on elementary reactions of ions that achieve complete catalytic cycles under thermal conditions. The examples chosen cover aspects of catalysis pertinent to areas as diverse as atmospheric chemistry and surface chemistry. We describe how transfer of oxygen atoms, bond activation, and coupling of fragments can be mediated by atomic or cluster metal ions. In some cases truly unexpected analogies of the idealized gas-phase ion catalysis can be drawn with related chemical transformations in solution or the solid state, and so improve our understanding of the intrinsic operation of a practical catalyst at a strictly molecular level.